In a medical milestone, a second patient has successfully received a genetically modified pig kidney transplant, offering new hope for those suffering from end-stage kidney disease.
Tim Andrews, a 66-year-old resident of Concord, New Hampshire, underwent the transplant at Massachusetts General Hospital on January 25 as part of an FDA-approved study exploring xenotransplantation—animal-to-human organ transplants. After a successful procedure, Andrews was discharged on February 1 and remains in the Boston area for monitoring before returning home.
Doctors report that the transplanted kidney is functioning normally, producing urine and maintaining stability, marking another step forward in the effort to address the chronic organ shortage in the U.S.
A Potential Solution to the Organ Shortage Crisis
Andrews had been on dialysis for more than two years, facing grim odds of receiving a human kidney. According to his transplant team, he had only a 9% chance of securing a donor kidney within the next five years and was at risk of being removed from the transplant list due to deteriorating health. The scarcity of available organs remains a major challenge—nearly 90,000 Americans are currently waiting for a kidney transplant, but only around 27,000 procedures were performed in 2023.
Xenotransplantation could provide a viable alternative. The pig kidney used in Andrews’ surgery was developed by eGenesis, a biotechnology company specializing in genetically modified organs. Scientists used CRISPR gene-editing technology to remove three pig proteins that typically trigger immune rejection, introduced seven human genes to improve compatibility, and disabled harmful pig viruses within the organ’s genome.
Building on Previous Successes
This breakthrough follows the first pig kidney transplant performed on 62-year-old Richard Slayman in March 2024. Although Slayman recovered well, he passed away two months later from causes unrelated to the transplant, according to his doctors.
Andrews’ case differs in one key aspect: he was selected as a healthier candidate with less severe kidney disease than Slayman. While Slayman had been on dialysis for eight years and had a history of heart disease, Andrews’ shorter dialysis period and stronger cardiovascular system could improve his chances of long-term success.
“Xenotransplant represents a turning point by eliminating organ shortage as a barrier to transplant,” said Dr. Leonardo Riella, medical director for kidney transplantation at Massachusetts General Hospital. “It offers a solution far superior to dialysis.”
Like Slayman, Andrews received an experimental immunosuppressant drug called tegoprubart, designed to prevent organ rejection. The drug, developed by Eledon Pharmaceuticals, is currently being tested in multiple clinical trials for kidney transplantation.
The Future of Xenotransplantation
Andrews is just the second of three patients set to receive genetically modified pig kidneys as part of this groundbreaking study. Meanwhile, other biotech firms are also advancing xenotransplant research. In February, the FDA approved the first large-scale clinical trial of pig kidneys, which could involve up to 50 patients.
Beyond kidneys, researchers are exploring the potential of transplanting pig hearts. Studies involving baboons have shown remarkable progress, with some surviving over 500 days with genetically modified pig hearts—far longer than originally expected. These promising results suggest that in the future, pig hearts could become a long-term solution for human transplant recipients.
For now, Andrews’ progress will be closely monitored, and his recovery could pave the way for the next two patients in the trial.
“The first time I saw Tim in the clinic, he was frail and struggling with complications from diabetes,” Dr. Riella said. “Dialysis was taking a severe toll on his body, and his path to a human kidney transplant was uncertain.”
But just days after the surgery, Andrews walked out of the hospital hand-in-hand with his wife, a symbol of hope for thousands still waiting for a second chance at life.
“This isn’t just one patient’s success,” Riella added. “It’s a step toward making xenotransplantation a widespread solution to the organ shortage crisis.”
